对长趾辽宁鸟的重新认识(英文)

A REVISED LOOK AT LIAONINGORNIS LONGIDIGITRUS (AVES)

早期发现于中国东北热河群的今鸟类化石多呈高度零散保存,本文对于惟一已知的长趾辽宁鸟( Liaoningornis longidigitrus) 标本的研究表明,该分类单元实际上是反鸟类的成员。虽然材料保存较差且破碎,但缺失发达的胸骨、胫骨脊和退化的脚爪,显示其应该被排除于更为进步的鸟胸类( ornithothoracines) 之外。辽宁鸟与所有已知的反鸟均有显著不同,但显示了与西班牙发现的 Eoalulavis hoyasi 的相似性: 它们相似的胸骨特征表明二者可能存在较密切的关系,尽管与其他反鸟类的不同表明,这可能是个体发育造成的假相。由于辽宁鸟标本过于零碎,因此目前难以确定其在反鸟类系统发育中的位置。

Many of the earliest discovered omithurine birds from the Jehol Group in northeastern China are highly fragmentary; this current study on the only known specimen of Liaoningornis longidigitrus, first described by Hou in 1997, indicates the taxon is in fact a member of Enantiornithes. Although based on fragmentary and poorly preserved material, the absence of a well-developed sternum, lack of developed cnemial crests on the tibiotarsi and reduced pedal unguals suggests Liaoningornis should be excluded from the more advanced ornithothoracine clade. The taxon remains distinct from all known en- antiornithines, although it shows similarity to the Spanish taxon Eoalulavis hoyasi ; shared features of the sternum suggest a close relationship between these two, although disparity from other enantiornithines suggests this may be an artifact of ontogeny. The only Liaoningornis specimen is too fragmentary to be able to make strong inferences about its placement within the diverse enantiornithine clade.